This attack works against Pattern Lock, PIN, Password, and Face Unlock. There is no way to secure your phone against your home screen being accessed.

Notes

HOWTO

Lock the device with a "secure" pattern, PIN, or password.

Activate the screen.

Press "Emergency Call".

Press the "ICE" button on the bottom left.

Hold down the physical home key for a few seconds and then release.

The phone's home screen will be displayed - briefly.

While the home screen is displayed, click on an app or a widget.

The app or widget will launch.

If the widget is "direct dial" the phone will start ringing.

Limited Scope

It's true, this attack is of limited value. That's one of the reasons why I've disclosed it.

Making a call relies on the phone having a direct dial widget on the home screen.

Running the apps is also of limited use - they go into the background immediately. If the app performs an action on launch (like recording from the microphone, switching on the flash, playing music, interacting with a server) that action will occur.

There is also the privacy concern that an attacker could see what apps you have installed on your homescreen - or see your calendar / emails if you use a widget which displays them.

Rapidly tapping the home button will - depending on your launcher - allow you to see what is on every home screen. Using an external video camera you should be able to clearly see all the user's calender & email widgets if they have enabled them.

Target

I've only tried this on one class of handset. Galaxy Note II N7100. Running 4.1.2 - the latest UK variant.
The two devices both ran the stock launcher and lock screen.
One device was rooted - the other was factory fresh.

I have not tested on any other devices.

Defending Yourself

This attack works against Pattern Lock, PIN, Password, and Face Unlock. There is no way to secure your phone against your home screen being accessed.

Your options are:

Do not use direct dial widgets on your homescreen.

Remove any calendar or email widgets which may show sensitive information from your homescreens.

Ensure that any apps which you do have on your homescreens do not automatically cost you money or act maliciously when launched.

Use an app locker to prompt for a password when apps are launched.

Changing to a different launcher will not protect you.

Using a 3rd party lock screen will not protect you if it accesses the emergency dialer.

Responsible Disclosure

Samsung don't have a dedicated responsible disclosure team. Nor do they offer a bug bounty.
The nearest I've found is this unlisted email address.

I spoke to several external security people, and Samsung relationship managers within the industry, who have raised the issue directly with Samsung. I also tried emailing Samsung directly. I know that people within Samsung have been made aware of this bug.

Despite that, five days later, and Samsung's security team have not made any contact with me to discuss this bug or its disclosure.
I wonder if this is typical of Samsung's attitude towards their customers and the industry in general? Do they believe that if they ignore problems, they will disappear?

[...] that a fix is on the way. The person who discovered it – an Android enthusiast by the name of Terence Eden – reported it five days ago, but Samsung has yet to issue any kind of response to the [...]

Just FYI the same issue was found and disclosed back in February by MTI, with some additional ways to exploit it. They used an S3 in their test, but was the same flaw in Samsung's version of Android. Might be useful to reference it for additional info for visitors. Thanks.

Thanks for that, I hadn't found anything similar. For those who are interested, the report is a vulnerability with S-Voice. It appears you can get the voice commands (Samsung's Siri) to call numbers etc even when the screen is locked.

I couldn't get it to work with my Galaxy Note II - so I don't know whether Samsung have fixed it.

Not worried at all. Don't have any sort of lock on my phone at all. Nobody should have anything "risky" on their home screen anyway! You only increase the chances of somebody having a go at someone else's phone by publicising it!

Interesting... My previous post was deleted.
So one more time:
If you setup a number in Emergency call / Emergency dialler / ICE - emergency contacts / Personal emergency contacts, you can call this number but the home screen is not anymore accessible, never shows again.
What is the problem with this information?

Hi, very interesting, in my case it is working. Maybe I am an exception, but no chance to reach the home screen, so I am happy, just wondering, why some Note 2 are acting differently. I am on Stock ROM and rooted. Regards.

I own a simlock free Samsung Galaxy Note II, not rooted, 4.1.2. I am observing the same behaviour as Terence. My 14 char password now seems nearly pointless (I am a security guy).

PS I didn't buy this phone because I thought it would be secure, but because my company's customers and collegues also buy Android and iOS phones, and I like to know what I'm talking about.

I had a voicemail icon on my homescreen. By clicking it (phone locked) I was able to dial that without having to enter my password; this definitely poses a security/privacy/commercial risk. So I moved the icon to another screen (i.e. off my home screen).

However, I just found out that I can also swipe to other screens while the phone is locked. So I was able to call voicmail anyway. I have now deleted the voicemail icon.

I have an icon for the flashlight which I can succesfully switch on or off with a locked phone (this could be considered a feature). Also I am able to start "Gallery", but do not see any pictures (after unlocking one can observe that the app is running in task manager).

So far I have not been able to start any other app while the phone is locked, but I wouldn't be surprised if more information can be accessed.

[...] has come across the bug that affects the Galaxy Note 2 and posted an article about the issue on his own blog, because he found out that the South Korean company lacks a dedicated disclosure team. There are [...]

[...] Eden, a UK-based mobility expert, wrote about and uploaded a video demonstrating the bug on his personal blog yesterday. As you can see in the video posted below, Eden locks his device’s screen before [...]